News crews from two television stations were robbed of cameras Thursday morning and a camera operator was pistol-whipped as they reported on a homicide at Pier 14 in San Francisco.

The mugging happened at 6:03 a.m. at the pier along the Embarcadero and was captured in part on the air.

KTVU reporter Cara Liu was reporting live when someone ran up and stole camera equipment belonging to KNTV, which also had a crew on the scene. During the incident, KNTV camera operator Alan Waples was pistol-whipped.

KTVU anchor Brian Flores was introducing the story and preparing to go live to Liu when she appeared startled and said, "Hold on, hold on, wait," before disappearing from the screen, as KNTV reporter Kris Sanchez and camera operator Alan Waples, 54, were being robbed at gunpoint by a young man.

The assailant came up behind Waples, who was was adjusting Sanchez's lighting, and put a gun to his head.

"Don't shoot! Don't shoot!" Sanchez yelled.

Waples said, "Take the camera!" He recalled later that he was waiting for the click of the gun.

"I thought he was going to kill Alan," Sanchez said.

The man then threw him to the ground and hit him with the gun in the ear, causing a large gash and leaving a big bruise on his upper arm.

All of this unfolded quickly as KTVU was broadcasting live, although the incident wasn't audible.

"Cara, you still there?" Flores asked.

"Sorry, there's an incident out here," she replied as she and KTVU photographer Keith Crook left to tend to the stricken KNTV crew.

"What's going on out there, Cara, doing OK?" Flores asked.

When she did not respond, Flores told viewers, "OK, looks like there's some type of incident going on with Cara Liu out there, not exactly sure what is going on. … Let's try to get more information on what's going on with Cara. Hopefully, she's doing OK, first off."

The robber stole a camera and tripod belonging to KNTV and struggled to put it in a black BMW, before hitting Waples one more time and telling Sanchez to get on the ground, she said. The man took KTVU's camera and tripod and fled, leaving behind an ammunition clip.

"There's no time for anything to go through your mind," Waples said. "When he was gone, it was a relief."

Crews from KRON and KGO-TV were also there but weren't robbed.

The crews were reporting on the shooting death Wednesday evening of a 31-year-old Pleasanton woman at Pier 14.

The incident is the latest in which news crews have been accosted by robbers in the Bay Area. The heists have prompted many stations to hire security guards to accompany crews, particularly for stories in Oakland. Many of the guards are former police officers.

The KTVU news crew has been victimized previously.

Crook was attacked in February and robbed of a live transmission unit and a microphone while reporting from a Hayward donut shop on a story about the lottery.

Last August, Liu was hit in the head by a woman while working a story about the shooting death of a man by private security guards at an East Oakland swap meet.

Henry K. Lee and Hamed Aleaziz are San Francisco Chronicle staff writers. E-mail: [email protected] and [email protected] Twitter: @henryklee @haleaziz